Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 407 | Thousand metric tons | NA |
| 2004 | 401 | Thousand metric tons | -1.47% |
| 2005 | 346 | Thousand metric tons | -13.72% |
| 2006 | 453 | Thousand metric tons | 30.92% |
| 2007 | 453 | Thousand metric tons | 0.00% |
| 2008 | 450 | Thousand metric tons | -0.66% |
| 2009 | 400 | Thousand metric tons | -11.11% |
| 2010 | 350 | Thousand metric tons | -12.50% |
| 2011 | 420 | Thousand metric tons | 20.00% |
| 2012 | 430 | Thousand metric tons | 2.38% |
| 2013 | 450 | Thousand metric tons | 4.65% |
